1. Field of the Invention
The present invention relates to the hydroxycarbonylation of butadiene and/or derivatives thereof, into pentenoic acids, and more especially, to the hydroxycarbonylation of butadiene via catalyzed reaction with carbon monoxide and water.
2. Description of the Prior Art
One known process for the preparation of adipic acid, one of the two basic constituents of nylon or polyamide 66 polymers, comprises the double carbonylation of butadiene or derivatives thereof.
Although it may be envisaged to carry out the two hydroxycarbonylations to convert butadiene into adipic acid in a single step, in actual practice it transpires that the two reactions must be carried out successively, if it is desired to obtain sufficiently high selectivities as to provide an economically viable industrial process.
U.S. Pat. No. 3,509,209 describes the hydroxycarbonylation of various olefins, including butadiene, via reaction with carbon monoxide and water, in the presence of hydrochloric or hydrobromic acid and a palladium-containing catalyst, at a temperature of 15.degree. C. to 300.degree. C. and at a pressure of 1 to 1,000 bar, preferably from 10 to 200 bar.
Under the reaction conditions described, it is observed that the yields of pentenoic acids are very low and that, indeed, very often the compound obtained is valerolactone.
FR-A-2,529,885 describes a process for the preparation of beta,gamma-unsaturated acids such as pentenoic acids, by carbonylation of a conjugated diene (more particularly butadiene) in the presence of water, a halogenhydracid, a palladium-based catalyst and a quaternary onium salt of an element selected from among nitrogen, phosphorus and arsenic.
This process gives good results, but it requires the use of a relatively large amount of a quaternary onium salt, which compound is expensive and the presence of which tends to complicate the final treatment of the mixtures at the end of the reaction.